The materials to be used for the proposed studies are: lung epithelial cells of the Oregon newt Taricha granulosa and endosperm from the African blood lily Haemanthus katharinae. The observations on living cells are to be combined and previously correlated with the studies in EM and immunocytochemical localization of microtubules. We have recently found that the mitotic spindle is composed of two functionally autonomous and independent half spindles comparable to the extensively studied monopolar spindle. Furthermore, the spindle in all stages of division is a fast oscillating system. The purpose of the proposed study is to characterize the structure and function of a "minimum" spindle, i.e., a spindle which is still functional but has a greatly reduced number of microtubules. The depletion of microtubules will be accomplished by drugs and low temperature (still within the physiological range). The effect on chromosome migration and especially oscillatory movements will be studied. The results would tell us whether the spindle operates as a single or multiple microtubular system. We will characterize the movements in spindles where: (1) kinetochore microtubules are the only spindle elements present and (2) astral spindles are devoid of one aster. The information should permit an understanding of spindle integrity and specifically illucidate the role of asters and spindle poles during mitosis.